<!DOCTYPE html>
<html>
<head>
    <title>贪吃蛇 Snake v2.4</title>
    <style>
        body{
            font-size:9pt;
        }
        table{
            border-collapse: collapse;
            border:solid #333 1px;
        }
        td{
            height: 10px;
            width: 10px;
            font-size: 0px;
        }
        .filled{
            background-color:blue;
        }
    </style>
</head>
<script>
    function $(id){return document.getElementById(id);}
    /**************************************************************
     * javascript贪吃蛇 v2.4 <br />
     * v2.4修正了蛇身颜色可以随着蛇前进而移动
     **************************************************************/
    //贪吃蛇类
    var Snake = {
        tbl: null,
        /**
         * body: 蛇身，数组放蛇的每一节，
         * 数据结构{x:x0, y:y0, color:color0},
         * x,y表示坐标,color表示颜色
         **/
        body: [],
        //当前移动的方向,取值0,1,2,3, 分别表示向上,右,下,左, 按键盘方向键可以改变它
        direction: 0,
        //定时器
        timer: null,
        //速度
        speed: 250,
        //是否已经暂停
        paused: true,
        //行数
        rowCount: 30,
        //列数
        colCount: 30,
        //初始化
        init: function(){
            var colors = ['red','orange','yellow','green','blue','purple','#ccc'];
            this.tbl = $("main");
            var x = 0;
            var y = 0;
            var colorIndex = 0;
            //产生初始移动方向
            this.direction = Math.floor(Math.random()*4);
            //构造table
            for(var row=0;row<this.rowCount;row++){
                var tr=this.tbl.insertRow(-1);
                for(var col=0;col<this.colCount;col++) {
                    var td=tr.insertCell(-1);
                }
            }
            //产生20个松散节点
            for(var i=0; i<10; i++){
                x = Math.floor(Math.random()*this.colCount);
                y = Math.floor(Math.random()*this.rowCount);
                colorIndex = Math.floor(Math.random()*7);
                if(!this.isCellFilled(x,y)){
                    this.tbl.rows[y].cells[x].style.backgroundColor = colors[colorIndex];
                }
            }
            //产生蛇头
            while(true){
                x = Math.floor(Math.random()*this.colCount);
                y = Math.floor(Math.random()*this.rowCount);
                if(!this.isCellFilled(x,y)){
                    this.tbl.rows[y].cells[x].style.backgroundColor = "black";
                    this.body.push({x:x,y:y,color:'black'});
                    break;
                }
            }
            this.paused = true;
            //添加键盘事件
            document.onkeydown= function(e){
                if (!e)e=window.event;
                switch(e.keyCode | e.which | e.charCode){
                    case 13: {
                        if(Snake.paused){
                            Snake.move();
                            Snake.paused = false;
                        }
                        else{
                            //如果没有暂停，则停止移动
                            Snake.pause();
                            Snake.paused = true;
                        }
                        break;
                    }
                    case 37:{//left
                        //阻止蛇倒退走
                        if(Snake.direction==1){
                            break;
                        }
                        Snake.direction = 3;
                        break;
                    }
                    case 38:{//up
                        //快捷键在这里起作用
                        if(event.ctrlKey){
                            Snake.speedUp(-20);
                            break;
                        }
                        if(Snake.direction==2){//阻止蛇倒退走
                            break;
                        }
                        Snake.direction = 0;
                        break;
                    }
                    case 39:{//right
                        if(Snake.direction==3){//阻止蛇倒退走
                            break;
                        }
                        Snake.direction = 1;
                        break;
                    }
                    case 40:{//down
                        if(event.ctrlKey){
                            Snake.speedUp(20);
                            break;
                        }
                        if(Snake.direction==0){//阻止蛇倒退走
                            break;
                        }
                        Snake.direction = 2;
                        break;
                    }
                }
            }
        },
        //移动
        move: function(){
            this.timer = setInterval(function(){
                Snake.erase();
                Snake.moveOneStep();
                Snake.paint();
            }, this.speed);
        },
        //移动一节身体
        moveOneStep: function(){
            if(this.checkNextStep()==-1){
                clearInterval(this.timer);
                alert("Game over!/nPress Restart to continue.");
                return;
            }
            if(this.checkNextStep()==1){
                var _point = this.getNextPos();
                var _x = _point.x;
                var _y = _point.y;
                var _color = this.getColor(_x,_y);
                this.body.unshift({x:_x,y:_y,color:_color});
                //因为吃了一个食物，所以再产生一个食物
                this.generateDood();
                return;
            }
            //window.status = this.toString();
            var point = this.getNextPos();
            //保留第一节的颜色
            var color = this.body[0].color;
            //颜色向前移动
            for(var i=0; i<this.body.length-1; i++){
                this.body[i].color = this.body[i+1].color;
            }
            //蛇尾减一节， 蛇尾加一节，呈现蛇前进的效果
            this.body.pop();
            this.body.unshift({x:point.x,y:point.y,color:color});
            //window.status = this.toString();
        },
        //探寻下一步将走到什么地方
        pause: function(){
            clearInterval(Snake.timer);
            this.paint();
        },
        getNextPos: function(){
            var x = this.body[0].x;
            var y = this.body[0].y;
            var color = this.body[0].color;
            //向上
            if(this.direction==0){
                y--;
            }
            //向右
            else if(this.direction==1){
                x++;
            }
            //向下
            else if(this.direction==2){
                y++;
            }
            //向左
            else{
                x--;
            }
            //返回一个坐标
            return {x:x,y:y};
        },
        //检查将要移动到的下一步是什么
        checkNextStep: function(){
            var point = this.getNextPos();
            var x = point.x;
            var y = point.y;
            if(x<0||x>=this.colCount||y<0||y>=this.rowCount){
                return -1;//触边界，游戏结束
            }
            for(var i=0; i<this.body.length; i++){
                if(this.body[i].x==x&&this.body[i].y==y){
                    return -1;//碰到自己的身体,游戏结束
                }
            }
            if(this.isCellFilled(x,y)){
                return 1;//有东西
            }
            return 0;//空地
        },
        //擦除蛇身
        erase: function(){
            for(var i=0; i<this.body.length; i++){
                this.eraseDot(this.body[i].x, this.body[i].y);
            }
        },
        //绘制蛇身
        paint: function(){
            for(var i=0; i<this.body.length; i++){
                this.paintDot(this.body[i].x, this.body[i].y,this.body[i].color);
            }
        },
        //擦除一节
        eraseDot: function(x,y){
            this.tbl.rows[y].cells[x].style.backgroundColor = "";
        },
        paintDot: function(x,y,color){
            this.tbl.rows[y].cells[x].style.backgroundColor = color;
        },
        //得到一个坐标上的颜色
        getColor: function(x,y){
            return this.tbl.rows[y].cells[x].style.backgroundColor;
        },
        //用于调试
        toString: function(){
            var str = "";
            for(var i=0; i<this.body.length; i++){
                str += "x:" + this.body[i].x + " y:" + this.body[i].y + " color:" + this.body[i].color + " - ";
            }
            return str;
        },
        //检查一个坐标点有没有被填充
        isCellFilled: function(x,y){
            if(this.tbl.rows[y].cells[x].style.backgroundColor == ""){
                return false;
            }
            return true;
        },
        //重新开始
        restart: function(){
            if(this.timer){
                clearInterval(this.timer);
            }
            for(var i=0; i<this.rowCount;i++){
                this.tbl.deleteRow(0);
            }
            this.body = [];
            this.init();
            this.speed = 250;
        },
        //加速
        speedUp: function(time){
            if(!this.paused){
                if(this.speed+time<10||this.speed+time>2000){
                    return;
                }
                this.speed +=time;
                this.pause();
                this.move();
            }
        },
        //产生食物。
        generateDood: function(){
            var colors = ['red','orange','yellow','green','blue','purple','#ccc'];
            var x = Math.floor(Math.random()*this.colCount);
            var y = Math.floor(Math.random()*this.rowCount);
            var colorIndex = Math.floor(Math.random()*7);
            if(!this.isCellFilled(x,y)){
                this.tbl.rows[y].cells[x].style.backgroundColor = colors[colorIndex];
            }
        }
    };
</script>
<body onload="Snake.init();">
/*************************************************************<br />
* javascript贪吃蛇 v2.4<br />
**************************************************************/<br />
<table id="main" border="1" cellspacing="0" cellpadding="0"></table>
<input type="button" id="btn" value="开始/暂停" />点左边按钮或按Enter开始/暂停游戏<br />
<input type="button" id="reset" value="重新开始" /><br />
<input type="button" id="upSpeed" value="加速" />点左边按钮或按Ctrl + ↑加速<br />
<input type="button" id="downSpeed" value="减速" />点左边按钮或按Ctrl + ↓减速
<script>
    $('btn').onclick = function(){
        if(Snake.paused){
            Snake.move();
            Snake.paused = false;
        }
        else{
            Snake.pause();
            Snake.paused = true;
        }
    };
    $("reset").onclick = function(){
        Snake.restart();
        this.blur();
    };
    $("upSpeed").onclick = function(){
        Snake.speedUp(-20);
    };
    $("downSpeed").onclick = function(){
        Snake.speedUp(20);
    };
</script>
</body>
</html>